FIG. 4 illustrates a prior-art chain saw 10 having a guide bar 12 equipped with a chain tensioner. The bar 12 is mounted to the housing 14 of the chain saw on studs 16 and 18. The bar 12 has a mounting slot 20 that receives the studs 16 and 18 and permits the guide bar 12 to be moved toward and away from a drive sprocket 22 as indicated by arrow 24. The guide bar 12 is moved toward the drive sprocket 22 to permit mounting a saw chain 26 in the edge groove 13 of the guide bar 12 and onto the drive sprocket 22. After the chain 26 has been mounted on the drive sprocket 22 and the guide bar 12, the guide bar 12 is moved away from the drive sprocket 22 to tension the chain 26 to its proper operating condition. When the guide bar 12 has been moved outwardly from the drive sprocket 22 to the desired position, lock nuts 28 and 30 are tightened on the studs 16 and 18 to lock the guide bar 12 in position. (The reader will appreciate that whereas two studs are desirable to control the movement of the bar, locking may be achieved with only one locking nut.)
The guide bar 12 has a mounting slot 20 that extends through the guide bar 12, that is, through the outer laminates 36, 38 and the center laminate 34 thereof to permit mounting the guide bar 12 onto the studs 16, 18 of the chain saw 10. The slot 20 provided in the outer laminates 36, 38 has a width that corresponds closely to the diameter of the studs 16, 18. A formed slot of the center laminate 34 has a channel-like portion 40 and a circular portion.
The guide bar 12 is initially mounted on the studs, 16, 18 of the chain saw 10 with the studs 16, 18 being received in the slot 20 of the guide bar 12. Nuts 28, 30 are loosely installed on the studs 16, 18 (or alternatively on only one of the studs) permitting the guide bar 12 to be slidably movable along the studs 16, 18 as indicated by arrow 24. The guide bar 12 is initially moved toward the drive sprocket 22 to permit mounting the saw chain 26 onto the drive sprocket 22 and the guide bar 12 in the conventional manner. This will require that the rack 48 be moved away from the end 21 of the slot 20 by rotating the pinion 60. When the saw chain 26 is properly entrained around the drive sprocket and the guide bar 12, the guide bar 12 is moved outwardly away from the drive sprocket 22 by utilizing the chain tensioner. A tool suitable for rotating the pinion 60 such as the tip of a flat bladed screwdriver is inserted through the aperture 46 and into the slot 64 of the pinion 60. The pinion 60 is rotated such that the rack 48 will be forced against the stud 16. Further rotation of the pinion 60 will force the guide bar 12 to move away from the drive sprocket 22. When the guide bar has been moved a sufficient distance away from the drive sprocket 22 to provide the proper operating tension of the saw chain 26, nuts 28 and 30 are tightened onto the studs 16, 18 to clamp the guide bar 12 to the housing 14.
The embodiments described and illustrated utilize the stud 16 (also referred to herein as the “mounting stud”) which projects from the housing 14 and is typically threaded and is intended for aligning and affixing the guide bar relative to the housing. The present invention utilizes this threaded stud as a convenient bearing member. It will be appreciated, however, that other projections provided on the housing 14 such as a formed box for bar alignment only or even a projection specifically provided as a bearing member is encompassed by this invention.